Device for supplying blinking voltage



Oct. 4, 1960 J. E. STELL 2,955,249

DEVICE FOR SUPPLYING BLINKING VOLTAGE Filed NOV. 12, 1958 Fig. 7 F\ l8(A.C)

-c 22(A.C.) T 24(110.)

Fig. 2

I m Voltage Positive I Feedback 5 Current Off Trip L Negative Feedback F Current A B C Time INVENTOR.

JAMES E. STELL United States Patent Oliice srgnments, to the United States of America as represented by the Secretary of the Navy Filed Nov. 12, 1958, Ser. No. 773,528 1 Claim. (Cl. 323-89) This invention relates to magnetic amplifiers and more particularly to their use in the generation of an intermittent or blinking output.

In using blinking voltage to alarm, for example, signal lamp circuitry, used in special control applications, it is desirable that the apparatus be shock-proof and relatively free from burnout and repairs. Magnetic amplifiers, having no vacuum tubes may be modified by the circuitry of this invention to provide such apparatus.

In accordance with this invention, a standard magnetic amplifier is employed having the usual negative feedback winding and positive feedback winding. The negative feedback winding is in circuit with RC circuits which are so designed that a slow increase and decrease of current through the negative feedback winding is effected for generation of a blinking output whereas the positive feedback winding is in an almost pure resistive circuit. It is the use of fast positive and slow negative feedbacks in the magnetic amplifier with their associated circuitry which provides the basis for the invention.

The principal object of the invention is to provide a device for the generation of a blinking or intermittent output by modifying the circuitry of a standard magnetic amplifier.

Another object of the invention is to provide a device for the generation of a blinking or intermittent output with associated circuitry which and a slow negative feedback.

In order that the present invention may be more readily understood, it will now be described with reference to the accompanying drawings wherein:

Fig. 1 is a circuit diagram of a preferred embodiment of the invention; and

Fig. 2 is a graphical representation showing amplitudes of output voltage and feedback currents versus time.

Referring first to the circuit diagram of Fig. 1, there is shown generally by broken lines a magnetic amplifier at having its load windings 12 and 12' connected to one pole 14 of an alternating current supply while the other pole 16 is connected to an A.C. terminal 18 of a full wave rectifier 20. The rectifier 20 has another A.C. terminal 22 and a pair of D.C. terminals 24 and 26. The magnetic amplifier 10 has a negative feedback control winding 32, a positive feedback control winding 34 and magnetic amplifier core shown at 28.

The magnetic amplifier is of a basic external-feedback type wherein the positive feedback control winding 34 aids the direct current control action of the input current whereas the negative feedback control winding 32 opposes or degenerates control conditions. By the invention the negative feedback control winding 32 receives voltage from an RC circuit comprising resistor R1 and capacitor C, connected as shown in the drawing, and the positive feedback winding 34 is fed from a D.C. terminal of the full wave rectifier 20. A resistor R3 is placed between D.C. terminal 26 and the positive feedback winding 34 and a pair of serial-1y connected unidirectional or rectifying valves 36 and 38 is placed between the load windings 12 and 12'. Rectifying valves 36 and 38, which may be composed of selenium discs or copper-cuprous oxide discs, admit current substantially only one half of each alternating current wave resulting in a circulation of provides a fast positive 2,955,249 Patented Oct. 4, 1960 pulsating current therethrough. Conductor 39 is provided for the negative half cycles of the alternating current which are not permitted to pass through rectifying valves 36 and 38.

Tapped off from a junction 40 between rectifying valves 36 and 38 are two lines, one leading to the A.C. terminal 22 of the full wave rectifier 20 and the other to one end of load 42, the other end of load 42 being connected to the alternating current input line 16.

In operation, the positive half cycles of the alternating current input 14 passes through load winding 12, rectifying valve 36 and thence to the A.C. terminal 22 of full wave rectifier 20. Of course, the negative half cycles, repel-led by rectifying valve 36 pass into load winding 12. through conductor 39. The A.C. input line 16 feeds A.C. terminal 18, the currents flowing to and through rectifier 20 having a direction as shown by the arrows. The negative feedback winding 32 and positive feedback winding 34 are fed from rectifier 20, the currents having a direction as indicated by the arrows.

Referring to Fig. 2, when the input voltage is first ap plied at time A, the output voltage immediately increases to a maximum value, and the positive feedback current increases very rapidly with output because it is in an almost pure resistive circuit. The negative feedback winding receives its voltage through RC circuit comprising resistor R1 and capacitor C. The current in this winding increases gradually as capacitor C is charged until time B when the negative feedback reaches the off trip point. At this instant, the voltage output and positive feedback current rapidly decrease to a mini-mum value. The negative feedback gradually decreases as the capacitor C is discharged in RC circuit comprising resistor R2 and capacitor C until the on trip point is reached at time C. At this point the cycle repeats to provide a continuous intermittent voltage output at load 42.

The band widths between off trip and on trip depends on the amount of positive feedback and may be varied by changing the ohmic value of resistor R3.

The entire circuit may be so designed to provide an intermittent off output, i.e., the period when the output is not producing voltages is greater than the period when it is producing voltages, or conversely, an intermittent on output by changing the ohmic value of resistors R1, R2 and R3. The values of the resistors and the capacitor-will determine the period of the output. The presence of a negative bias may be found desirable in order to minimize the size of the capacitor C.

Having thus described the invention, what is claimed is:

A magnetic amplifier circuit for generating a blinking output which comprises a source of alternating current having two terminals, a pair of serially arranged load windings connected electrically to one of the terminals of said source, a pair of serially connected unidirectional valves connected in series between the load windings, a. full wave rectifier having one A.C. terminal connected to the other terminal of said source, a connection between said unidirectional valves and the other A.C. terminal of said rectifier, a load in circuit between the A.C. terminals of the rectifier, a positive feedback winding and a negative feedback winding connected in parallel with one D.C. terminal of said rectifier, a pair of RC circuits having a common capacitor connected between said negative feedback Winding and the other D.C. terminal of said rectifier and a resistor between said other D.C. terminal and said positive feedback.

References Cited in the file of this patent UNITED STATES PATENTS 

